Starch tabling process



July 1938. F. JEFFERIES STARCH TABLING PROCESS Original Filed April 26, 1933 mg gs Q a w 4 w MM .r @QEN Patented July s, 1938 UNITED STATES PATENT OFFICE. C

STARCH mama raocsss Frederick L. Jellerles, La Grange, Ill., assignor to International Patents Development Company, Wilmington, DeL, a corporation oi Delaware '1 Claims.

This invention relates 'to the manufacture of starch from corn and more particularly to the separation of the starch from the gluten by an operation known as tabling in which the mixture of starch, gluten and water, referred to as mill starch or starch milk (derived from the operations in which the germs, hulls and fibre are separated from the comminuted corn) is caused to flow through long narrow and shallow inclined troughs, called tables. upon which the starch is deposited and from the lower ends of which the gluten andbulk of the water in the mill starch overflows into tanks or gluten settlers" in which the'gluten is separated by subsidence from the water and from which the water, known as gluten water", is siphoned off, and, according to modern practice, is returned to the starch making process for re-use and the ultimate saving of the solid substances, mostly com solubles, contained therein.

The present invention provides an improvement upon the heretofore customary method of tabling the mill starch, which improvement involves delivering the mill starch to the table heads at a much higher density, 1. e. lower water content than has heretofore been the practice or has been considered possible, together with certain changes in operating conditions, which have been found necessary, or at least desirable, when the table head densities are in-' creased to the extent contemplated by the invention. The purposes of this change in tabling practice are first to make possible a substantial reduction in the volume of gluten water issuing from the gluten settlers, which becauseof its high content of solubles and micro-organisms should be discharged to rivers and streams as sparingly as possible, if at all, and if returned to the process, for the prevention of stream pollution, economy of water, and recovery of solubles, should be distributed to certain places in the system where the micro-organic activity which the gluten water return promotes will be as little detrimental as possible-an object facilitated by the reduction in volume of the gluten water; second, to improve the separation between the starch and gluten, so that there will be less gluten in the starch and less starch in the gluten; and third, to reduce the amount of tabling and settling equipment and the time required for these operations. This application is a division of my co-pending application, Serial No. 668,095, filed April 26, 1933, for Manufacture of starch (issued August 3, 1937 as U. S. Patent 2,088,706) and the invention was described in substance, if not in all details, in application filed by the inventor, April 22, 1932,- SerlalNo. 606,897, for Manufacture of starch from corn (issued December 22, 1936 as U. S. Patent 2,065,313). I do not claim the herein described improved method of tabling when combined with the other process steps described and claimed in the aforesaid earlier applications; the present application seeking to claim the novel and vimproved tabling process by -itself for application to any starchmaking system in which it can be used advantageously.

The invention is illustrated in the accompanyingdrawing which is a diagram showing the operations of tabling the starch, settling the gluten and washing the starch.

Referring to the drawing, l designates one of the starch tables; 2 the common trough for receiving the gluten and water from a number of adjacently arranged tables; 3 the trough for receiving the starch when flushed from the tables, the more common method used at the present time for removing starch from starch tables; 4 one of' the gluten settlers; 5 the press for removing the water remaining in the gluten after the bulk of the gluten water has been siphoned oil; 6 and l the starch washing filters; and 8 the dilution tank in which the starch is diluted between filtering operations.

The mill starch is discharged to the upper or head end of the tables through pipe 9. The starch is deposited on the tables in the form' of long, thin wedges which are thickest at the table heads. The gluten and water are discharged from the ends of the tables into the troughs 2, as indicated by the arrow I0. From the trough 2, the gluten and water are discharged through conduit it into the gluten settlers. Here the gluten subsides. The 'gluten water is drawn oil through conduit 12, and the gluten passed through conduit iii to the press 5 from which the relatively dry gluten is discharged, as indicated at it, the water being returned to the gluten settlers through conduit IS.

The starch deposited on the tables is removed by flushing water discharged to the table heads from pipe 16. The flushing water may be fresh water or alight process water such as the wash water derived from the washing of the starch on filters to be described. The flushing water is circulated repeatedly over the tables, the water returning from the trough 3 to the table heads through pipe l'l, until a starch suspension of proper density has been reached, whereupon this relatively heavy liquor is discharged through pipe ll to the first filter 6, where the starch is de-watered and then washed with fresh water entering the system through pipe IS. The washed starch stripped from filter 6 is vdischarged through conduit 28 to the dilution tank where it is mixed with water discharged into the tank through branch pipe 2| of the fresh water line. The diluted starch passes through conduit 22 to the second filter I where the starch is again I de-watered, and then washed with fresh water introduced throughbranch pipe". The pipe l6, which brings the flushing water to the table heads, is shown as a branch from the wash water discharge pipe 24 of filter I. The discharge pipe 24 connects with the wash water discharge pipe 25 from the first filter 6. Ordinarily the wash water in pipe 25 is returned to the starch making process for re-use. The solids which tail of! with the major portion of the water in the mill starch may consist of somewhat more than onehalf gluten, that is protein, the rest being mostly starch. The starch from the tables, when washed, should contain but a fraction of one per cent of protein; and by the statement in the claims that substantially. all of the gluten is separated from the starch, it is not intended to imply that the starch may not contain such starch to remove the gluten therefrom is an ex-.

pedient which has been used for a great many years and for a long period of time hasbeen the accepted method of separating gluten from starch in corn starch factories. For many years it has been the practice to table the mill starch at densities between 5 and 7 Baum. It has been the general belief or assumption throughout the industry and for many years prior to the present invention that to bring about a. proper separation of the gluten from the starch on the starch tables, the densities of the mill starch should not be in excess of about 7 Baum or at the most 8 Baum. In some factories tabling densities have been as low as 5 or 5 /2" Baum. The applicant, however, has discovered that it is possible to table mill starch at very much increased table head densities and to get as good a separation between the starch and gluten, in fact even a better separation, than with the lighter liquors. For example, by passing smaller volumes of the mill starch over the tables per unit of time and increasing the pitch of the tables, it is possible to satisfactorily table a mill starch liquor of 13 Baum or even of 15 Baum, and to get a better separation, that is, less starch in gluten and less gluten in starch, than has heretofore been obtained by tabling at densities of 5 to 7 Baum. Starch tables in different factories may differ somewhat in length, width and pitch. Ordinarily the tables are about 110 feet long, 2 feet wide, and have a pitch of about 5 inches from end to end. Under these conditions the mill starch (5 to 7 Baum) is ordinarily delivered to the tables at approximately three gallons per minute per table. In accordance with the present invention with tables as described (but having a pitch 11 Baum, the rate of delivery to the tables may be somewhat more rapid, say 2.0 gallons per minute. For a, 15 Baum liquor the rate may be 1.2 gallons. For a density of 8 Baum the supply should be about 2.5 gallons per minute. It will be obvious that these figures are only approximate and are based upon table dimensions and table pitch as stated. Approximately the rate of delivery to the tables should be in inverse ratio to the density of the liquor, assuming that the tables are the same. In order to get the best results, however, the pitch of the tables should be increased over that which has been customary; that is. the pitch of' the tables should vary directly as the density of the mill starch.- In reference to pitch, in order to get the best results, the usual pitch of 5 inches-that is, the table heads 5 inches above the ends of the tables-should be increased to 12 inches for a liquor of 15 Baum. That is the pitch ratio should be increased within the range 1-264 to 1-110 depending upon the density of the mill starch treated. For liquor of 13 Baumthe pitch should be about inches.

If attempt be made to table mill starch at densities substantially greater than those of standard practice, delivering the mill starch to the table heads at the same rate and'with the tables pitched to the same inclination as prescribed by standard practice, it will be found that the amount of starch tailing off with the gluten will be increased and also the amount of gluten deposited with the tabled starch. That is, the separation is less eflicient bothfrom the point of view of starch in gluten and from the pointof view of gluten in starch. The increase instarch in gluten is apparently due to the fact that the starch particles, which constitute the major portion of the solids in the magma, being closer together in the higher density mill starch, subside to the table, or to the accumulated starch on the table, less readily than in the case of "a more dilute magma. The increased deposit of gluten is apparently due largely to the shrinkage in volume of the mill starch, as it flows down the table, because with the higher density mill starch the proportion of water to solids is diminished.

By increasing the pitch of the tables a faster flow results which can be made to compensate for the shrinkage in volume so that all of the gluten, within working. tolerances, will be car'- ried over the ends of the tables, giving a tabled starch of the requisite high purity. However, under these conditions, i. e. increased density. in-

rate of delivery to the tables, the tendency of the starch, due to the increased density of the mill starch, to tail off with the gluten is enhanced 1 creased pitch of the tables, but no change in the l Bydecreasing the rate of delivery of the mill starch to the table heads, without changing the table pitch from that of standard practice, less starch will tail off with the gluten because the streams of mill starch flowing over the tables vantageously only where it is not important to produce a starch of the highest purity, that is of gluten. In'fact the new practice has resulted in reduced protein 'in starch and reduced starch in gluten. By decreasing the rate of delivery of the mill starch to the table heads, the flow of the magma over the tables is in shallower streams preventing the starch from tailing off with the gluten, despite the higher density of the magma. By increasing the pitch of the tables these shallower streams are made to move more rapidly, which prevents the gluten from being trapped by the tabled starch, the surface of which is never perfectly even but is likely to be more or less channelled by the flow thereover of the mill starch liquor.

Theoretically at least, the diminution in depth of the streams could be effected by using wider tables instead of by decreasing the rate of flow per minute per table. However, practical considerations have determined within approximate limits the width of starch tables, and consequently it is much more practical to decrease the rate of delivery to the table heads in proportion ap-v proximately to the increase of the density of the mill starch liquor treated.

It. will be understood that the specific figures of gallons of mill starch supplied to the table heads per minute are based, for practical reasons on a table inclination of 10 inches. Theoretically there should be a different table pitch for each density,- but this is hardly practical for actual factory conditions. width of the table are necessarily factors and change of table length or width will necessarily involve corresponding adjustment of the factors of gallonage to the table heads and pitch of the tables. The above directions will make it possible, however, for anyone skilled in the art to work out for tables of any'suitable length and width, the proper rate of flow and the proper pitch for any given density of mill starch substantially above the range of 5-7 Baum used in former practice, and, consequently, to adapt the present invention 'to varying conditions. The exact figures will depend also upon whether the ultimate desideratum is the reduction to a minimum of gluten in the starch or the reduction to a minimum of starch in the gluten. By referring to the density of the mill starch as being substantially in excess of 7 Baum, the customary maximum in former practice, I intend densities of the order of say 11 to 15 Baum and at least appreciably greater than 8 Baum.

It is the intention to claim here all modifications within the scope of the appended claims.

I claim:

1. In the manufacture of starch. from com: the improvement which consists in tabling the mill starch at a density between 8 Baum and Moreover, the length and 15 Baum, delivering the same to the table heads at a rate (in the case of tables feet long, 2 feet wide having a pitch not substantially less than 5 inches)- varying from substantially 2.5 gallons per minute per table for an 8 Baum density to 1.2 gallons per minute for a 15 Baum density.

2. In the manufacture of starch from corn: the improvement which consists in tabling the mill starch at a density between 8 Baum and 15 Baum, delivering the same to the table heads at a rate (in the case of tables 110 feet long, 2 feet wide) varying from substantially 2.5 gallons per minute per table for an 8 Baum density to 1.2 gallons per minute for a 15 Baum density; with the tables pitched at an inclination of 5 inches, from end to end, for a density of 8 Baum varied to 12 inches for a density of 15 Baum.

3. In the manufacture of starch from com: the improvement which consists in tabling the mill starch at a density of substantially 13 Baum, delivering the mill starch to the table heads (in the case of tables 110 feet long and 2 feet wide) at a rate of approximately 1.8 gallons per minute per table, with the tables having a pitch of approximately 10 inches from end to end.

4. In the manufacture of starch from com: the improvement which consists in tabling the mill starch at a density between 8 Baum and 15 Baum, delivering the mill starch to the table heads (in the case of tables 110 feet long and 2 feet wide) at a rate not substantially in excess of 2 gallons per minute per table, and varying the pitch of the tables within the range of 5 to 12 inches, to counteract the tendency of the gluten to deposit with the starch. I

5. In the manufacture of starch from com: the improvement which consists in tabling the mill starch at a density substantially above 7 Baum and decreasing the rate at which the mill starch is delivered to the tables and increasing the pitch of the tables, from the rate and pitch, respectively, used in tabling 7 Baum mill starch, in proportion, substantially, to the increase in density of the mill starch over 7 Baum.

6. In the manufacture of starch from com: the improvement which consists in tabling mill starch at a density between 8 Baum and 15 Baum, and delivering the starch to the table heads in a volume per unit of time approximately proportioned inversely, to the density of the mill starch, with the tables pitched to an extent approximately in proportion, directly, to the mill starch density.

'i. In the manufacture of starch from corn the improvement which consists in tabling mill starch at a density substantially above 7 Baum, and delivering the starch to the table-heads in a volume per unit of time approximately proportioned inversely to the density of the mill starch,

with the tables pitched to an extent approximately in proportion, directly, to the mill starch density.

FREDERICK L. JEFFERIEB. 

